The invention relates to metal halide and mercury arc lamps and to the thermal control of a metal halide or mercury arc lamp in operation through the use of a directed air flow.
The invention in general relates to the thermal control of an arc lamp in operation and more specifically to the use of a directed air flow to the arc chamber of the lamp.
In the prior art it is common to use arc lamps with a reflector to form an assembly which are used in an enclosed housing to provide directed light which is used for projector systems and the like. When used in an enclosed housing, an arc lamp generates high internal heat which can result in short lamp life and high lamp infant mortality rate due to the localized heat generated by the lamp in combination with a reflector within the confines of the enclosed housing. In these instances, venting and laminar flow cooling techniques are often employed to lower thermal values such that system installation is possible. Yet, in systems of this type it is common that highly loaded arc lamps exhibit a short life of 200 hours and a high infant mortality rate of less than 100 hours with an average life of approximately 400 hours or 20-45% of rated life. Lamp life times of this duration are unacceptable and result in high replacement cost to the ultimate user and discourage their use in systems of the type described above.
In addressing the problems described above, the prior art has believed and been taught away from directing any coolant air flow directly onto the lamp chamber in that such an approach would be unsatisfactory, and result in instability of lumen output and color. There has therefore been a continuing need in the field for a system which would allow for extended lamp life without compromising stability of lumen output or color for arc lamps used in the systems described above.
It is therefore an object of the present invention to provide a method of lamp thermal control which overcomes the problems of the prior art described above.
It is a further object of the present invention to provide for a method of lamp thermal control which results in improved lamp life.
It is another object of the present invention to provide a method for increasing lamp life without compromising stability.
It is yet another object of the present invention to provide a method of thermal control in which the arc lamp achieves thermal equilibrium in a relatively short time.
It is a further object of the present invention to provide a method for the thermal control of an arc lamp through the directed air flow to the interior at the lamp chamber and surrounding reflector.
It is a further object of the present invention to provide a method of increasing the life of an arc lamp assembly.
It is yet a further object of the present invention to provide for lamp thermal control for an arc lamp positioned in an enclosed chamber which utilizes controlled direct air flow directly around and past the lamp chamber.
The present invention is directed to situations where a lamp assembly, which includes an arc lamp and a reflector, is used in an enclosed housing or as a sealed module which acts as a high intensity light source.
In the present invention, an ambient air flow is allowed to flow into the interior volume defined by the reflector geometry, and pass over the lamp chamber at a critical angle from the vertical. Lamp thermal control is effected, resulting in a dramatic increase in lamp life and a reduction in infant mortality of the lamp. The process of the present invention overcomes the problems of the prior art in systems of this type, in that lamp failure caused by the early onset of devitrification of the lamp chamber and quartz to foil hermetic seal separation are eliminated. Through the use of this process the anode temperature dropped approximately 50-70xc2x0 C., and the cathode temperature dropped approximately 30-40xc2x0 C. By employing this invention lamp life is improved by a factor of 3.